The announcement angered some existing Glass owners. Some demanded a free upgrade to the 2GB version in comments on the posting. Others said they would be willing to pay a small fee for an upgrade, while one acknowledged that if further hardware updates were planned, it wouldn't make sense for Google to upgrade all users each time. "Getting a final consumer version would be swell though," he added.

Google does not plan to upgrade existing users' devices, it said.

"Throughout our open beta program, you can expect to see us make changes here and there. We won't be swapping devices, but you'll continue to see improvements with our software updates," a Google representative said in a comment on the posting.

The company does replace broken or defective Google Glass devices, however, prompting Google Plus user Jake Weisz to identify a loophole in the no-upgrades policy. "If defective Glass units get free upgrades to 2GB, you will see a lot of 'defective' models this month," he wrote.

In May, Google broadened its Explorer Program, making Glass available in the U.S. to anyone over 18 years old for US$1,500. Before that, users who wanted to buy Glass required an invitation from Google. On Monday it extended the offer to U.K. residents over 18, who can purchase Glass for £1,000.

Google is upgrading the Glass software as well as the hardware. It is adding an easier way to frame shots for photos, with the addition of L-shaped corners bracketing the image in the viewfinder screen, and adding two new Google Now cards, one to remind users where they parked their car and another to let them know when packages are arriving.

The company also announced 12 new Glassware apps from partners, including Shazam, a music recognition app that can be triggered with the words "OK Glass, recognize this song," and 94Fifty Basketball, a training aid that works with a sensor-equipped basketball to offer feedback after each shot.

Google's announcements arrived just before the start of its annual I/O developers conference in San Francisco, which kicks off Wednesday. The company will lead sessions on how to build new types of software for Glass during the conference.

Google is also expected to unveil a small TV set-top box resembling the Apple TV and Amazon's Fire TV at the event, the Wall Street Journal reported on Wednesday. Citing two people who have seen the device, the newspaper said the device will not be sold under the Google brand but will be powered by the Android TV software that Google developed to play games, movies and other content on TVs. Users will be able to control the box with their Android phones and tablets and maybe with other devices, the report said.